Teegarden's Star has been found
in astronomical images taken
more than 50 years ago.

The star was initially thought to be located only around 7.6
(+ 3.3 / -1.8) light-years (ly) away from Sol, based on a
preliminary trigonometric parallax of 0.43 +/- 0.13 arcseconds
(") or 2.3 +1.0 / -0.54 parsecs. Its unusual dimness and
relative metal abundance indicated, however, that the star was
probably further away, perhaps around 11.7 ly or more based on
an inferred, spectrophotometric parallax of 3.6 +/- 0.4" --
see discussion below and at
RECONS).
According to Sky
and Telescope (April 2004), Todd J. Henry, the director
of RECONS,
reported a recent distance estimate of 3.82 parsecs (or 12.5
ly). In June 2004, George Gatewood, the director of the
Allegheny Observatory,
also reported a similar, initial parallax estimate of 0.259 +/- 0.004
arcseconds (AAS
204th Meeting session abstract), for a distance of 3.86 +/-
0.06 parsecs (12.6 +/- 0.2 ly), a distance modulus of 2.067+/- 0.034 magnitudes,
and an absolute visual magnitude of 17.47 +/- 0.04
(A.O.
summary)
-- "in excellent agreement with those of the
U.S Naval Observatory
(Conrad Dahn, private communications)." In 2006, a new
estimate of 12.52 +/- 0.13 ly was reported by
RECONS
(Henry
et al, 2006b; and
(Henry
et al, 2006a), but a revised estimate of 12.59 light-years (based on 0.2593 arc-seconds was reported in 2009
(Gatewood and Coban, 2009)

Teegarden's Star was initially
estimated to lie only around 6.5
to 10.1 light-years from the Solar
System (more from
GSFC).

Teegarden's Star is located in the southwest corner (2:55:10.6+16:17:1,
J2000; or 2:53:0.5+16:52:58, ICRS) of Constellation
Aries,
the Ram. It can be found southeast of
Hamal
(Alpha Arietis),
Sheratan
(Beta Arietis),
Mesarthim
(Gamma Arietis), and spiral galaxy
M 74;
northeast of
Alrescha
(Alpha Piscium); and northwest of
Lamda,
Mu, Xi2, and Nu Ceti, and
Menkar
(Alpha Ceti) and
Kaffaljidhma
(Gamma Ceti). If the initial distance estimate had been
confirmed, the star would have become the new third-closest
system to Sol after Alpha Centauri
3 and Barnard's Star. Like
all red dwarf stars, however, Teegarden's Star is too faint
to be seen with the unaided Human eyes from Earth.

Teegarden's Star appears to
be a very dim, red dwarf star
of spectral and luminosity
type M6.5 V
(more).

Initial measurements of the spectrum of Teegarden's Star
and its tangential velocity (of 52.9 +/- 11.7 kilometers
per second) suggest it is a main-sequence dwarf star of
spectral and luminosity type M6.5-7.0 V. Such a cool red
dwarf star is substantially smaller and dimmer than Sol,
currently estimated to have only around eight percent of Sol's
mass, around one-seventh of its diameter, and 1/300,000th
of its visual luminosity. If the preliminary distance
measurement had been correct, then the star would be
underluminous by a magnitude of 1.2 +/- 0.7 (three times
dimmer than similar stars of its type), although the
relative strengths of the star's spectral bands of Calcium
Hydride (CaH2) and Titanium Oxide (TiO5) provide no evidence
that it is metal-poor.

Teegarden's Star has around
eight percent of Sol's mass
and is 300,000 times fainter,
which is why it was not found
until September 2002 despite
its proximity to the Solar
System (more from
GSFC).

The star's relative distance to Sol has been revised as
initial estimates of magnitude and distance indicated that
the star had an unreasonably small diameter of 68 percent
of Jupiter. Subsequent measurements of magnitude and
metallicity suggested that the star is actuallyed located
around 11.7 ly away, based on an inferred,
spectrophotometric parallax of 3.6 +/- 0.4 arcseconds
(Teegarden
et al, 2003) -- more discussion at
RECONS.
A more precise measurement of the star position to improve
the determination of its trigonometric parallax distance
was launched by the U.S. Naval Observatory. In June 2004,
George Gatewood (Director of the
Allegheny
Observatory) also reported a similar, initial parallax
estimate of 0.259 +/- 0.004 arcseconds
(AAS
204th Meeting session summary), for a distance of 3.86
+/- 0.06 parsecs (12.6 +/- 0.2 ly), a distance modulus of
2.067+/- 0.034 magnitudes, and an absolute visual magnitude
of 17.47 +/- 0.04
(A.O.
abstract) -- "in excellent agreement with those of the
U.S Naval Observatory
(Conrad Dahn, private communications."
Useful catalogue numbers for this star include:
SO025300.5+165258, SO25300.5+165258, SO J025300.5+165258,
2MASS J02530084+1652532, APM EO0425-0315372, LSPM J0253+1652, and USNO-B1.0 1068-00028941 or USNO-A2.0 1050-00774305.

Closest Neighbors

The following star systems are
probably located within 10 light-years of Teegarden's Star.

Around 1800 BCE, the relatively dim stars of Constellation
Aries, marked the coming of Spring for Humans of
Earth's northern hemisphere. One myth of the Ancient Greeks
associated with Aries, the Ram, involved the God Hermes who
sent Aries to save the life of Prince Phrixus. The Ram
carried Phrixus to a land near the Black Sea called Colchis
(the capital of which was Aea) and asked to be sacrificed
to the Gods and to have his Golden Fleece be given to King
Aeetes. For more information about the stars and objects in
this constellation, go to Christine Kronberg's
Aries.
For another illustration, see David Haworth's
Aries.

For more information about stars including spectral and luminosity
class codes, go to ChView's webpage on
The Stars of
the Milky Way.